What defines 'viscous hydroplaning'?

Viscous hydroplaning occurs when the runway surface is covered by a film of moisture that creates a significant reduction in friction between the tires and the runway. This phenomenon typically happens when there is a thin layer of water on the runway, causing the tires to lose direct contact with the asphalt or concrete surface and instead ride on this moisture barrier.

The lack of direct contact leads to decreased braking effectiveness and can complicate the handling of the aircraft during landing and rollout phases. Understanding viscous hydroplaning is crucial for dispatchers and pilots to ensure safety during operations in wet conditions. This background on the mechanics of hydroplaning helps in assessing weather conditions and their impact on aircraft performance.

Other choices provide definitions for different scenarios that do not accurately capture the specific mechanics of viscous hydroplaning. For instance, while standing water can contribute to hydroplaning, it refers more specifically to dynamic or full hydroplaning conditions rather than the viscous type caused by a thin film of moisture.